Apparatus for separating slag from a slag containing molten metal



Filed Feb. 2, 1951 Nov. 17, 1953 l ARTER, JR.

H ET AL APPARATUS FOR SEPARATING SLAG FROM A SLAG CONTAINING MOLTEINMETAL ZSheets-Sheet l INVENTORS fsaac Harier; Jr: &' BY YEmp/eWfiatc/ife ATTORNEY Nov. 17, 1953 l. HARTER, JR. ET AL 2,659,120

APPARATUS FOR SEPARATING SLAG FROM A SLAG CONTAINING MOLTEN METAL FiledFeb. 2, 1951. 2 Sheets-Sheet 2 ATTORNEY Patented Nov. 17, 1953 UNITEDSTATES PATENT OFFICE APPARATUS "FOR SEPARATING SLAG FROM' A SLAGCONTAINING MOLTEN METAL Application February 2, 1951, Serial No.209,164-- 3 Claims.

The present invention relatesiin general-to the casting of metals, andmore particularly to the pouring of molten slag-containingmetals. Thisapplication is a continuation-in-part of our application filed January13, 1948, Serial Number 2,114, now Patent No- 2,571,033.

In the casting of metals containing slag contaminants, it is desirableto eliminate or reduce thecontaminants to the lowest degree possible 7ularly prevalent in theproduction offerrousalloy castings such as steel.Ferrous metals are customarily melted under slagging conditions, and, asis also well known, the metals readily oxidize in contact with air atmolten metal temperatures and chemically react with practically all ofthe'known refractory materialsin contact therewith, forming ferrous andferric compounds collectively known as slag.

The presence of slag contaminants in the molten ferrous metalsdeliveredto a continuous casting mold, as an example, is particularlydeleterious'due, in the main, to their insulating value. In thecontinuous castingprocess, any slag carried into the mold with themolten metal will tend to collect on the periphery of the casting. Thiswill tend to insulate the contiguous portion of the-casting wall fromthe heat removal effect of the adjacent mold, sothatthe shell strengthof the casting may be insufficient to withstand the ferrostatic pressureimposed thereon, resulting in a rupture of the casting shell. It hasalso been observed that where the solidification of a portion of thecasting is delayed, eventhough rupture of the wall does 'not occur; thesubsequent solidification of the interior portion of the castingfrequently results in an'unequal circumferential cooling of the castingand the formation of shrinkage cracks or voids in a portion of thecasting.

The art is well aware of the adverse effects of metal splashing in toppouring metal into a mold, but its deleterious effect is accentuated inthe continuous casting of metals wherein the general cause of splashingis closely related to other problems more specific to a continuouscasting :process. Splashing is commonly caused bythe improper deliveryofmetal from an exces- 2 c sive height above a moldand in anoff-centered location with respect to the axis of the mold. In

continuous casting, an off-center delivery of mol-I ten metal and/or anexcessive height of metal fall to the level of the molten metal withinthe mold not only causes .splashing, but also encourages turbulence ofmetal within the mold which tends .to prevent the formationof a.circumferentially uniform wall thickness. It is also beneficial toreduce the length of all of the mol ten stream'in order to reduce thechance of metal oxidation.

The principal object of the present invention istoprovide apparatus forthe controlled delivery of molten metal to a casting mold. A furtherandmore specific'object is to provide: apparatus of the characterdescribed for the separation of slag contaminants from molten ferrousalloys and the delivery of clean metal to a casting mold. An additionalspecific object is to provide apparatus of the character describedcapable of delivering a.v stream of substantially slag-free molten metalto a continuous casting mold under regulated conditions'of deliveryposition and a substantially uniform molten metal delivery velocity.

The various featuresiof novelty'which characterize our invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages andspecific objects attained by its use,reference should be had to'the accompanying drawings and descriptivematter in whichwe have illustrated and described anembodiment of ourinvention.

Of the drawings:

Fig. l is an elevation, partly in section, ofa tun dish and itsoperating mechanism constructed inaccordance with the present inventionas interposed between a tilting ladle source of molten metal andacontinuous casting mold;

Fig- 2'is'an elevation', in section, of the tun dish;

Fig. 3' is :an elevation, in section, of a modified formof tun dishtaken on line 3-3 of Fig. 4;

Fig. 4 is a plan view of the tun dish shown in Fig. 3;

Fig. 5 is a section taken on the line 5-5 of Fig. 3; and

Fig. 6 is an end elevation, as'viewed from the right of Fig. 3.-

While various features of the present invention are adapted foruse inthe casting of metals, the apparatus herein: described is particularlyadvantageous for use in the continuous casting :of carbon and alloysteels and other slag-forming metals.

In the continuous casting of metal, the molten metal, such as steel orother metal or alloy is introduced into the upper end of an uprightmold, solidified therein by heat exchange with a cooling fluid andwithdrawn from the opposite lower end of the mold. The molten metal isdelivered to a holding and pouring ladle it from which it is poured at aselected rate and an optimum temperature through a pouring lip in oneside thereof into a tun dish H for delivery into a continuous castingmold assembly E2. The ladle l2 shown schematically in Fig. 1 in its relsor p with the tun dish and the mold assen The ladle is arranged fortilting motion a' J a horizontally disposed axis of rotation cleaned bytrunnions l3 projecting outwardly on opposite sides of the ladle body.The position of the ladle I- is also adjustable in a horizontaldirection so that the stream of metal discharged from the ladle may beselectively positioned while the rate of discharge therefrom isregulated by the angle of ladle tilt.

The tun dish H of the present invention is arranged to receive themolten metal from the ladle Ill and to discharge the metal into the openend of the mold assembly 12. The mold asse bly includes, in general, avertically elongated molding tube l4 encircled by a horizontall disposedflange member l5 at its upper end. An annular fluid chamber is surroundsthe upper end of the tube is as defined by the flange 5, a transverseplate member 19 and an outer cylindrical wall H. An inner cylindricalsleeve l8 is spaced from the outer surface of the tube Hi and extendsupwardly from the member [6 to a position spaced from the flange !5. Acylindrical skirt 20 extends downwardly from a position adjacent theupper end of the sleeve l8 in closely spaced relationship with themolding tube It to define an annular cooling fluid flow passageway 21therebetween substantially the length of the mold. An annular perforateddistributing plate 22 is positioned intermediate the height of thechamber 18 between a plurality of cooling fluid inlets 23 and a flaredinlet 26. of the passageway 2i. With this construction the molten metalis solidified in the mold assembly by heat exchange through the tube Mto a high velocity stream of cooling fluid passing through thepassageway 2 i.

Experience has shown that the most satisfactory casting results areattained by the delivery of molten metal to the center of a pool ofmolten metal maintained in the upper portion of the molding tube in asubstantially slag-free condition and under substantially uniform flowconditions. Best casting results are obtained with a low velocity ofmolten metal delivery. The temperature of the metal and the rate of itsdelivery is obtained by proper control of the pouring ladle it, but theaccurate regulation of optimum metal delivery position within the moldis determined by adjustment of the tun dish ll. The tun dish is alsoconstructed and operated to minimize the inclusion of slag in thecontinuous casting and to provide a maximum visibility of the metalwithin the mold.

The tun dish H is shown in detail in Fig. 2 and consists of a metallicouter casing 32 having an inner refractory lining 32a and a layer ofinsulating material 32?) interposed between a major portion of theliningand the casing. The tun dish H is divided into an inlet chamber 25and a smaller outlet chamber 26 by a transverse vertical refractorybafiie 0r partition 2?. The chamber 26 and part of the chamber 25 iscovered by a movable refractory top 29. A transverse inclined refractorybaille section 28 is located in the inlet chamber 25 and extends upwardat an angle of approximately -30, with its lower end merging into thevertical partition Z'l. The lining and baffles are made of any suitablehigh temperature refractory material. Holes 38 in the bottom of thevertical partition 27 below its junction with the inclined bafile 28form a plurality of separate passages, or in some cases a singlepassage, through which the molten metal can flow from the inlet to theoutlet chamber of the tun dish. A V-notch refractory weir 3! is formedin the end wall of the tun dish for the discharge of molten metal. Inoperation, the tun dish is preheated to a high temperature, normallytilted forwardly about 10 and positioned so that the stream of moltenmetal from the ladle It] falls into the inlet chamber and strikes thevertical partition 2? below the normal molten metal level therein atsuch an angle that the stream continues to descend until it strikes theinclined baille 28, which deflects the metal entrapped slag to thesurface. given to the molten stream and the entrapped slag is mostimportant because the slag being lighter endeavors to separate from theheavier metal and also readily adheres to other slag that has previouslycome to the surface. The slag-free metal then flows over the end of theinclined baiile 28 and through the passages 33 in the vertical baiile tothe outlet chamber 26, from which it flows over the V-notch weir 3i.

The described construction of the tun dish is eiiective in separatingslag from the molten metal delivered thereto, and is also eflective inmaintaining an essentially uniform velocity in the stream of metaldelivered to the mold assembly. This is largely accomplished by thebafiles 2? and 23, in that the stream or metal entering the chamber 25contacts a pool of molten metal therein which absorbs a major share ofthe:

velocity of the entering metal stream, with the stream thereafterreversing its direction of flow as directed by the baffles. The reversalin the direction of metal flow tends to absorb the remaining velocity ofthe entering metal stream. The flow of molten metal over the upper endof and beneath the baflie 28 toward the passages consequently movessubstantially under the in fluence of the difierence in metal headbetween the pools of metal in the inlet and outlet chambers. In thismanner, the velocity of the stream of metal entering the mold assembly[2 from the tun dish is at a minimum and is not appreciably influencedby changes in the metal velocity as delivered to the tun dish.

In operation, the molten metal is lip-poured from the ladle ill to enterthe previously described entrance and of the tun dish H and to dischargefrom the opposite end thereof into the mold it. The rate of molten flowinto the mold is ordinarily regulated by controlling the ladle It withthe angle of tilt of the tun dish maintained at an adjusted value duringthe pouring period. The partition 21 and the inclined baflie 28cooperate to divert the flow direction of the- The rising impetusv Theiiniescg'rao imergedpassageways 30: thetlowert'portiomzof .the partitioninto: the'soutleitchamber of the-stun dish. .LIn -this 'i'manner slag:is iseparated'. from the metal and the 'metal will idischargerfromathepouring lip of .theitun-rdishiundersubstantially uniform velocity-flowconditionszrinto thef fmold.

lit will be observed thatthe velocity. ofithe molten metal streamdelivered". to .thermold willfbermamtained at a generallyluniform flow;velocity head which is substantially independent oflthe:stream "velocityentering the tun .dish. .Such:flow*v'elocity conditions are'particularlyz-importantuin :a.:-continuous casting process,1 inv thatturbulence-within themold is largely .avoided and:optimum'icircumferential: uniformity: :of; metal:cooling.5:is:encouraged.

.wardly from opposite sides thereof. Thetun" dish is divided into three"connected chambersby spaced transversesubstantiallyupright partitionsit and H, with the intermediate chamber 12, between the bames l and H,having more-volume than the chambers l3..and 14 at the .inleteand outletend portions, respectively.

The inlet chamber 13 is provided with a rammed refractory bottom I5, asshown in Fig. 3, Where the upper surface is curved to receive adownwardly directed incoming stream of molten metal and to direct thestream upwardly and longitudinally toward the discharge end of the tundish. The partition H is provided with an opening 16 in the upperportion thereof adjacent one longitudinal side of the tun dish. Theopening it is restricted in cross-section flow area so that the streamof metal passing therethrough from the inlet chamber 13 into theintermediate chamber 12 will have sufficient velocity to cause theentrained slag to rise to the surface of the molten metal poolmaintained in chamber 12. Locating the opening 16 adjacent onelongitudinal wall of the tun dish also encourages the maintenance of arelatively quiescent pool of metal in the chamber 12 adjacent thepartition H removed from the opening 16.

The partition is provided with one or more port openings H thereinbetween the chambers '12 and i4 adjoining the bottom of the tun dish. Aninclined bafile 18, similar in location and function to the baffle 28 ofthe tun dish ll shown in Fig. 2, is positioned on the chamber 12 side ofthe partition 10 and extends transversely across the full Width of thechamber. The baffle I8 is upwardly inclined and merges with thepartition H3 at a position upwardly adjacent the port openings TI, toredirect the metal flowing downwardly along the partition 70 toward theupper surface of the molten metal pool therein so as to encouragefurther slag separation. The molten metal passing through the port 11into the chamber It must pass around the end of the baffle 18, and inits movement separation of entrained slag is encouraged, As a result,the metal discharging from the chamber 14 through the V-notoh weir issubstantially slag free.

With the construction described, molten metal delivered :thereto followsssan foyer-sand .u-nder ffiow:path.zinzimovingi.throughathe' -tunzdish.The stream of; molten metal entering the tun;idish:.65 from" the. ladlei0: strikes the: curved surface :of .thelbottomfli in the-inlet chamber13 r-and.-.-is .directed iman upward direction-through. the restrictedopening 16 in the baflie H. .Thexmolten metal. stream; rises tothe-surface of the; pool of im'etalz maintained" within the chamber :12.and .zwithvthe reduction inzflow: velocity-. -ingpassing itherethroughslag: will separate and accumulate onzthe 311001 surface. 'The.rseparatedaslag -.--.will tend to move toward .the partition 10. due1302 13116 impetus ofthe: entering" metal and the flow of metal.downwardly. along. the. surfaceof the partition would: entrain some.minor portion of .the accumulated slag withthe downwardly. .movingmetal. tHowever, athe .:bafiie -18 redirects uthe downwardly movingmetal stream. -in-an upward .direction, so that any. entrained-slag willbeagain .directed toward the surface. ofthe-pooLand-a the metal passingaround the end ofthe baffle' la toward-the port 11 and the chamber 14willbe substantially slag free.

As disclosed and claimed-in our co-pending application, Serial Number2,114, filed. January 13, 1948, the tun dish II or 65 is supportedatapredetermined elevation above the .mold.-.assem- .bly I2 by-an arm. 33.The arm is pivot'allyan ranged for movement a ,horizontal,.plane..so

.that .the tundishcan. be generally-positioned relative to the mold, andwhen not .in; .useithe arm and tun dish may be swungawaylfromithevicinity of the. mold. .A.. more accuratepositiming. of the tun dish:relative to the moldlis obtained by a plurality of adjusting movementsof the tun dish relative to the arm 33. These movements include tiltingthe tun dish about a horizontal axis intersecting the crest of the weir3|; angular movement of the tun dish in a horizontal plane about avertical axis; and a straight line lineal movement of the tun dish in ahorizontal plane. These motions are primarily for the purpose ofcorrecting any misalignment of the metal stream which may be caused byfrozen metal on the discharge lip of the tun dish or on the weir of thepouring ladle i0, and thus enable the operator to accurately direct thestream of metal into the center of the molten pool in the mold.

A metal platform or plate 36 is pivotally attached to the arm 33 anddirectly supports the tun dish by means of pedestals 31 carrying thetrunnion bearings 32. The pivotal connection between the arm and theplate is provided by a pivot pin closely fitted through the plate 33 andextending through a slotted opening in the arm 33. The pivot maintainsthe arm and plate in vertical relationship while permitting a horizontalrotational movement of the plate relative to the arm. The tun dish issupported by trunnions 4| extending outwardly from opposite sidesthereof and resting in the bearings 32 to provide an axis of tiltingrotation intersecting the crest of the V-notch weir. One of thetrunnions 4| is provided with a depending lever arm 42 keyed thereonwhich is contacted by a crank screw 43. The screw 43 is threaded througha block 44 fastened to the plate 36 so that the lever arm can be movedthrough an arc to regulate the angle of tilt of the tun dish.

While in accordance with the provisions of the statutes we haveillustrated and described herein the best form and mode of operation ofthe invention now known to us, those skilled in the 7 art willunderstand that changes may be made in the form of the apparatusdisclosed without departing from the spirit of the invention covered byour claims, and that certain features of our invention may sometimes beused to advantage without a corresponding use of other features,

We claim:

1. A tun dish comprising refractory walls defining a vessel having adischarge weir in an end wall thereof, at least one transverse partitionspaced from said weir and extending across said vessel and having atleast one port therethrough positioned adjacent the bottom of saidvessel, and an inclined baffle merging into the side of said partitionremote from said weir and above said port, said bafile projecting awayfrom said partition at an acuate angle to the portion of the partitionabove the battle, said bafiie extending far enough toward the wall ofthe vessel opposite the wall having the discharge weir to intercept anddeflect upwardly the stream of molten metal entering the tun dish.

2. A tun dish comprising refractory walls defining an open top vesselhaving a discharge opening in one end thereof, a transverse partition insaid vessel having a plurality of passageways therethrough positionedintermediate the ends of its lower portion, and an inclined transversebaiiie merging into the side of said partition remote from said enddischarge opening and above said passageways, said bafile projectingfrom said partition at an acute angle to the portion of the partitionabove the balile, said baffle extending far enough toward the wall ofthe vessel opposite the wall having the discharge opening to interceptand deflect upwardly the stream of molten metal entering the tun dish.

3. A tun dish comprising refractory walls defining a vessel having aV-notch weir in one end wall thereof, a transverse substantially uprightpartition spaced from said weir and extending across said vessel andhaving at least one port therethrough positioned adjacent the bottom ofsaid vessel, an inclined bafiie merging with said partition above saidport and projecting away from the weir end of said vessel at an acuteangle to said partition, and a second transverse partition extendingacross said vessel at a position spaced from said weir and said firsttransverse partition, said second partition having an opening in theupper portion thereof adjacent one of the side walls of said vessel.

ISAAC HARTER. J a. TEMPLE W. RATCLIFFE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 381,119 Devereux Apr. 17, 1888 463,514 Keiper q Nov. 17, 1891535,514 Van Riet Mar. 12, 1895 1,672,728 Otis June 5, 1928 1,813,381Carrington July 7, 1935 FOREIGN PATENTS Number Country Date 282 GreatBritain Aug. 22, 1912 333,384 Great Britain Aug. 14, 1938 92,514 GermanyJuly 2, 1897

